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Ta 2 O 5 thin films were fabricated by pulsed plasma-enhanced chemical vapor deposition (PECVD) with simultaneous delivery of O2 and the metal precursor. By appropriately controlling the gas-phase environment self-limiting deposition at controllable rates (∼1Å/pulse) was obtained. The process was insensitive to substrate temperature, with a constant deposition rate observed from 90to350°C. As-deposited Ta2O5 films under these conditions displayed good dielectric properties. Performance improvements correlate strongly with film density and composition as measured by spectroscopic ellipsometry and Fourier transform infrared spectroscopy. Pulsed PECVD eliminates the need for gas actuation and inert purge steps required by atomic layer deposition.

Plasma-enhanced chemical vapor deposition ͑PECVD͒ of zinc oxide was accomplished using diethyl zinc, oxygen, and argon in a capacitively coupled reactor. The plasma chemistry was studied by optical emission spectroscopy ͑OES͒ with particular focus on the effects of reactant composition and rf power. Process-property relationships were established by comparing plasma behavior with resulting film properties as characterized by the Hall effect, spectroscopic ellipsometry, and X-ray diffraction. In our studies of stoichiometry it was observed that the plasma chemistry was very similar to hydrocarbon combustion, so much so that the results were interpreted by borrowing the concept of the equivalence ratio, . For fuel-rich conditions ( Ͼ 1) deposition was dominated by incorporation of atomic Zn, the films were randomly oriented, and electrically insulating. In contrast fuel-lean conditions produced conducting films with a preferred ͑0 0 2͒ orientation. The results indicate that OES may be useful for calibrating oxide PECVD systems that employ bubblers to deliver organometallic precursors. It was also shown that increasing the plasma power had the same effect of decreasing , which was to drive the chemistry toward complete combustion. Electrical properties improved exponentially with both increased substrate temperature and decreased growth rate, highlighting the importance of surface migration in establishing carriers and controlling mobility.

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Tantalum oxide films were deposited by pulsed and continuous wave ͑CW͒ plasma-enhanced chemical vapor deposition ͑PECVD͒. The pulsed films were stoichiometric and free of impurities as measured by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. CW films contained significant amounts of hydroxyl impurities, resulting in a nonstoichiometric composition with an O/Ta ratio of ϳ2.8. Impedance spectroscopy was used to quantify ion transport through electrochromic half-cells formed by depositing tantalum oxide on both tungsten and vanadium oxides. Logarithmic plots of the imaginary component of impedance vs frequency were employed to extract equivalent circuit parameters. Despite the differences in composition the pulsed and CW films displayed similar ionic conductivities, with values of ϳ6 ϫ 10 −10 and ϳ2 ϫ 10 −10 S/cm for H + and Li + , respectively. However, the pulsed PECVD films displayed dramatically reduced electrical leakage. The ratio of ion/ electron conductivity exceeded 100 for pulsed PECVD films, while ion / e was Ͻ1 in CW material.